Diatomite/Cu/Al Layered Double Hydroxides Hybrid Composites For LDPE Degradation

Diatomite is a sedimentary rock formed with accumulation of single-celled diatom corpses,whose main component is amorphous silica.It has unique porous structure,many hydroxyl groups and hydrogen bonds on its surface,and excellent performance.On the other hand,layered double hydroxides?LDH?is a new type of layered inorganic functional material with robust properties,such as acid and alkali,interlayer anion exchangeability and so on.In this paper,diatomite,copper nitrate and other raw materials were used to prepare diatomite Cu/Al-LDH composite?DI-LDH?by hydrothermal method,and the sample was modified to get SDI-LDH.Then,the structure of DI-LDH was characterized by X-ray diffraction?XRD?,thermogravimetric-differential thermal analysis?TG-DTA?,fourier transform infrared spectrum?FTIR?,scanning electron microscope?SEM?and N₂adsorption and desorption?BET?.Based on this,the effects of reaction temperature,reaction time,experimental environment and catalyst content on the pyrolysis of LDPE catalyzed by diatomite,Cu/Al LDH,DI-LDH and SDI-LDH were studied.The pyrolysis process of LDPE was characterized by TG-DTA,TG-FTIR,XPS,flue gas analyzer and cone calorimetry.The research content is as follows:?1?High-crystallinity DI-LDH can be prepared by hydrothermal method.The best synthesis process of DI-LDH was that the reaction temperature was 110?ensure constant temperature for 12 h.And the optimum molar ratio of diatomite,copper nitrate and aluminum nitrate was 1:2:1.667.According to this method,diatomite and Cu/Al-LDH in DI-LDH were linked together by silanol functional groups.At the same time,the layered structure of Cu/Al LDH and porous structure of diatomite are preserved in DI-LDH,and the pore diameter of DI-LDH was 16%higher than that of Cu/Al LDH.The heat resistance of DI-LDH at low temperature was lower than that of Cu/Al LDH,and at high temperature was higher than that of Cu/Al LDH.?2?LDPE composite plates were prepared with LDPE as raw material,diatomite,Cu/Al LDH,DI-LDH and SDI-LDH as catalysts.The conversion of LDPE/SDI-LDH and LDPE/DI was 97%and 96%at 350?,the maximum degradation temperature was457?and 440?,the conversion of LDPE/DI-LDH was 97%and the maximum pyrolysis temperature is 449?,the conversion of LDPE/DI-LDH was 99%and the maximum pyrolysis temperature was 468?.SDI-LDH and diatomite have the best catalytic performance to reduce the pyrolysis temperature of LDPE.DI-LDH has certain catalytic performance,while Cu/Al LDH does not affect the pyrolysis temperature of LDPE.The optimum catalyst content of DI-LDH was 4%at 350?.When the reaction time was 2 h,the pyrolysis conversion of LDPE does not increase with the increase of reaction time and remains constant.Air atmosphere was more conducive to the pyrolysis of LDPE.Increasing the reaction temperature was helpful to the pyrolysis of LDPE.?3?The content of CO,CO₂ and CH₄ released during the diatomite,Cu/Al LDH and DI-LDH catalytic pyrolysis of LDPE were measured by flue gas analyzer.Cu/Al LDH was helpful to reduce CO emission which was reduced by 35%at the highest peak,and a large amount of CO and CO₂will be released during the pyrolysis of LDPE catalyzed by diatomite.DI-LDH can effectively reduce CO and CO₂ emission,which was reduced by30%and 15%at the highest peak.From the above results,we know that DI-LDH can effectively reduce the CO and CO₂ emissions during LDPE pyrolysis,and the catalytic performance of it was the best.